Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$174.46	9.856%	$191.6548	$191.65	$191.65	$191.70
Purchase #2	$225.51	4.318%	$235.2475	$235.25	$235.25	$235.20
Purchase #3	$33.30	12.415%	$37.4342	$37.43	$37.45	$37.40
Purchase #4	$37.28	12.470%	$41.9288	$41.93	$41.95	$41.90
Purchase #5	$105.37	3.278%	$108.824	$108.82	$108.80	$108.80
Purchase #6	$35.82	4.799%	$37.539	$37.54	$37.55	$37.50
Purchase #7	$179.45	3.453%	$185.6464	$185.65	$185.65	$185.60
7 purchase totals =	$791.19		$838.2747	$838.27	$838.30	$838.10